Variable radius crank arm for typewriter impression control

ABSTRACT

A variable radius crank arm which is selectively adjustable is disclosed in a typewriter setting and used to exert an influence on the flight of the typebar towards the print impression position for the purpose of controlling the velocity of the typebar at impact and hence the quality of the printed impression. The crank arms is provided with a selectively positionable clip which is retained in the selected position by appropriate detenting. The compactness of the design combined with the ease of accessibility for the purpose of adjusting the clip to the selected position is a feature of the invention. Another feature resides in the fact that the clip on the variable radius crank arm may be selectively positioned to any desired position without introducing undesired or detrimental effects in the positioning or placement of any other parts. This last feature is achieved by positioning the clip in an arcuate slot.

United States Patent Burlrett et al. I

[ 51 Mar. 28, 1972 154] VARIABLE RADIUS CRANK ARM FOR TYPEWRITER IMPRESSION CONTROL [72] Inventors: George Burkett, Monroe County; Thurston H. Toeppen, Dutchess County,

both of N.Y.

[73] Assignee: The Singer Company [22] Filed: Jan. 29, 1970 [2]] Appl. No.: 6,875

Primary Examiner-Robert E. Pulfrey Assistant Examiner-Stephen C. Pellegrino Att0rney--George W. Killian, Patrick J. Schlesinger, Charles R. Lepchinsky and Jay M. Cantor [57] ABSTRACT A variable radius crank arm which is selectively adjustable is disclosed in a typewriter setting and used to exert an influence on the flight of the typebar towards the print impression position for the purpose of controlling the velocity of the typebar at impact and hence the quality of the printed impression. The crank arms is provided with a selectively positionable clip which is retained in the selected position by appropriate detenting. The compactness of the design combined with the ease of accessibility for the purpose of adjusting the clip to the selected position is a feature of the invention. Another feature resides in the fact that the clip on the variable radius crank arm may be selectively positioned to any desired position without introducing undesired or detrimental effects in the positioning or placement of any other parts. This last feature is achieved by positioning the clip in an arcuate slot.

5 Claims, 2 Drawing Figures PATENTEDMAR28 I972 IIVVENTOR GEORGE BURKETT THURSTON H. TOEPPEN RELATED APPLICATIONS This application is not related to any other application in the sense of being a division, continuation, etc. However, there are other patents and applications which illustrate and describe related features. More specifically, this application is an improvement of the structure disclosed in U.S. Pat. No. 3,355,000, issued to E. O. Blodgett on November 28, 1967. An application filed on Nov. 28, 1969 by Richard W. Allen and assigned Ser. No. 880,820 and assigned to the same assignee as the present application discloses a related structure. Both of the cited references should be considered as incorporated herein to provide additional information relating to a more complete machine of a type in which the present invention may be incorporated. In addition, U.S. Pat. No. 2,700,446, issued to E. O. Blodgett on Jan. 25, 1955, should be consulted for a more complete description of a typical power driven typebar typewriting machine into which the present invention could be incorporated.

BACKGROUND OF THE INVENTION There is a constant efiort in all endeavors to produce things better, cheaper, faster, more reliable, more efficient, or with new and improved features, etc. The present invention was made as a result of a study undertaken to achieve one or more of the enumerated characteristics. More specifically, the invention was made as various techniques were studied to determine if they could be used to produce a printed impression of a higher quality, at an increased printing rate and with greater economy. The invention could be applied to a wide variety of mechanisms. The invention was originally conceived in connection with a printing machine and more particularly for use in a character-by-character typebar printer and therefore, the invention will be described in a typewriter setting. The speeds at which a machine incorporating the present invention is capable of operating, are available only when it is operated by automatic controls such as those disclosed in the cited Blodgett U.S. Pat. No. 2,700,446. That is, the machine is able to operate at a sustained rate considerably greater than the operating speed of a champion typist. A particular feature of the invention is that the structure provides a simple and convenient means for making adjustments to obtain an optimum print quality.

It is an object of the present invention to provide a new and improved connecting link and having a selectively variable lever arm.

It is a more specific object of the invention to provide a pivoting bellcrank assembly having a selectively positioned clip thereon which in all positions remains a predetermined distance from a single predetermined point.

It is another object of this invention to provide a linkage train wherein the effective lever arm of one element may be selectively altered without introducing any change into other elements of the train.

It is another object of the present invention to provide a new and improved typewriter.

It is another object of the invention to provide a structure for a typewriter which is adapted to the production of high quality printing.

It is yet another object of the invention to provide a typewriter structure which includes means for adjusting the impression of each individual character.

lt is another object of the invention to provide impression control means which are more compact, economical, accurate and more convenient than prior art techniques.

It is yet another object of this invention to provide individual impression control means for each character wherein the impression can be controlled in small increments over a wide range.

A very important factor in the appearance of the typewritten page is the matter of impression. Accordingly, many attempts have been made to control impression and to produce machines which produce consistent impressions with a given set of adjustments. For example, some prior art devices have been designed to control the momentum imparted to the typebar by controlling the contact between the power roll and the operating cam. Other techniques have involved the use of a tension spring to be engaged by an abutment fixed to the typebar during the terminal part of the typebar stroke. For this last mentioned means, the adjustment was usually obtained by bending a metal tab. Such mechanisms proved unsatisfactory in service as the metal tabs to be bent were relatively unaccessible and also it was not practical to achieve the desired preciseness of adjustment. More satisfactory structures using similar principles were designed and showed promise except that they were extremely complex and, therefore, were expensive to manufacture and maintain. Other improvements and/or modifications have been devised but have not been widely used for a variety of reasons including the fact that they tend to be expensive, difficult to adjust, fail to maintain adjustment, do not provide a sufficient range of adjustments, do not give consistent results and/or require more space than is available. The structure of the present invention overcomes these difficulties.

One of the problems encountered by the innovator considering the problem of impression control resides in the fact that the density of the components within the structure means that any modification must be very compact. Some prior art techniques solved the problem by providing a variety of parts which were individually selected to produce the desired results. However, changing the parts was a difficult and time consuming process and therefore, it was not unusual to accept a degraded impression quality rather than to expend the time and efiort to improve the impression quality. The structure of the present invention is sufficiently compact to fit into existing structures and provides the required range of adjustments without any need to remove and replace parts.

SUMMARY OF THE INVENTION The present invention uses a bellcrank as part of the driving linkage between the power roll and the typebar. The driving linkage is similar to that shown in the cited patent 3,355,000. The novel difference resides in the manner of coupling the linkage to the bellcrank. More specifically, the bellcrank now comprises two parts; the bellcrank itself and a clip which may be selectively adjusted to a plurality of positions. The link is coupled to the clip; and by adjusting the clip to a selected one of its plurality of positions the connection of the link relative to the pivot point of the bellcrank may be altered. By shifting the position of the link relative to the bellcrank pivot point, the leverage applied to operate the typebar may be modified and such modification of the link can alter the initial velocity of the typebar and hence the impact velocity and the impression.

A feature of the invention resides in the fact that the impression may be controlled by a single adjustment and not by a delicate balance between two or more adjustments. A further feature resides in the fact that the adjustments may be easily and quickly made from the top of the machine and does not require access or adjustment from the bottom.

The characteristics, structure and operation may be best understood from a consideration of the following description taken together with the drawing wherein:

FIG. 1 is a vertical section through a typical typebar writing machine showing the novel variable radius bellcrank and clip assembly constituting a presently preferred embodiment of the invention, and

FIG. 2 is an enlarged view of the variable radius bellcrank and clip assembly.

Referring now more specifically to FIG. 1, there is shown a typical typebar writing machine, i.e., a power driven typewriter, incorporating the present invention. FIG. 1 of this application is similar to FIG. 1 of U.S. Pat. No. 3,355,000, is-

sued to E. O. Blodgett on Nov. 28, 1967, and to FIG. 3 of U.S. Pat. No. 2,700,446, issued to the same E. O. Blodgett on Jan. 25, 1955. Both of the cited patents may be referred to for a more complete understanding of an entire writing machine into which the present invention may be incorporated.

The mechanism comprises a plurality of key buttons 101 each of which is associated with an individual keylever 102 which is pivoted on a pivot rod 103. Each keylever 102 and its individually associated key button 101 is biased by an individual spring 104 coupled between a hole 105 in the keylever 102 and a common bar 106 supported for rotational motion about pivot point 107. The springs 104 resist downward motion of a key button 101 and the associated keylever 102. The selected angular adjustment of bar 106 and its pivot point 107 controls the tension in springs 104 and thereby control the amount of pressure which must be applied to a key button 101 to pivot the associated keylever 102 about pivot rod 103 in a counterclockwise direction as viewed in FIG. 1. The upward motion of each keylever 102 is limited by an upstop 108.

The writing machine illustrated may be used in connection with a punched tape or punched card reader, or other appropriate associated equipment, to cause the automatic printing of characters without the manual operation of the key buttons 101. To this end there is included on each keylever 102 a pin 109 which may be engaged by a seeker 110 to pull down the keylever 102. The means by which the seekers 110 may be operated is more fully explained in the U.S. Pat. No. 2,700,446 patent.

Associated with each keylever 102 is a cam assembly 111 which is disposed on one side or the other of power roll 112 which rotates in the direction indicated by the arrow. Depending from each keylever 102 is an arm 113 to provide a mechanical connection between the keylever 102 and the associated cam assembly 111. Adjacent keylevers 102 are associated with cam assemblies 111 on opposite sides of the power roll 112. All cam assemblies are pivotally supported on an appropriate one of two fulcrum rods 114.

In response to the counterclockwise pivotal motion of one of the keylevers 102, the cam 115 is released and caused to engage the power roll 112 all as more fully set forth in U.S. Pat. No. 2,700.446 and in the manner familiar to those skilled in the art. The power roll 112 is rotated at a uniform velocity about its axis in the direction of the arrow and by power means not shown.

For convenience in distinguishing between the cam assemblies 111, it is customary to call those closest to the operator the front cam assemblies and the others rear cam assemblies. Accordingly, as seen in FIG. 1, the left hand cam assembly 111 is a front cam assembly. Except for minor differences in geometry, the front and rear can assemblies 111 are identical and all serve identical functions. For the present description, consideration will be given to the front (or left hand) cam assembly 1 1 1.

When the front cam assembly 111 is triggered into action, its cam 115 is released and contacts power roll 112 and this causes the front cam assembly 111 to be pivoted clockwise about fulcrum rod 114. As may be seen, an adjustable arm 1 17 extends from the cam assembly 111 and pivotally coupled to the end of adjustable arm 117 is an adjustable length link 118 which has a formed end 119 (see FIG. 2) which is coupled through a hole 120 in clip 121 which is held on variable radius bellcrank 122.

It must be understood that for each key button 101 there is an individual keylever 102, an individual cam assembly 111, an individual bellcrank 122 and an individual typebar 132. Two cam assemblies 111 are shown, but for clarity only one bellcrank 122 is shown. The illustrated bellcrank 122 is one associated with a front cam assembly 111. A bellcrank associated with a rear cam assembly 111 would also be pivoted at 103. As will be seen, the slot 151 of bellcrank 122 is arcuate having a center at approximately point 152 when the parts are in their at rest position. The equivalent slot in a bellcrank for a rear cam assembly 1 11 would have its center at approximately a point on the rear cam assembly 111 corresponding to point 152 on the front cam assembly 111.

Bellcrank 122 has a hole 126 through which pivot rod 103 passes. Accordingly, bellcrank 122 is supported on pivot rod 103 for pivotal motion of said bellcrank 122. As may be visualized from a study of FIG. 1, the clockwise pivoting of front cam assembly 111 on fulcrum rod 114 will result in a counterclockwise pivoting of bellcrank 122 about pivot rod 103.

Bellcrank 122 has an offset arm portion 127 which engages the operating lever 128 which is also pivotally supported by pivot rod 103. Accordingly, the referred to clockwise pivotal motion of front can assembly 111 will cause a counterclockwise pivotal motion of operating lever 128.

Coupled between the operating lever 128 and the depending arm 131 oftypebar 132 is a link 133.

The typebar is pivotally mounted and supported at pivot point 134. The typebar 132 carries a type slug 135 for producing a character on a document (not shown) which is supported by a platen (not shown) all in the manner familiar to those skilled in the art. It may now be seen that the clockwise pivotal motion of front cam assembly 111 will result in the clockwise pivotal motion of typebar 132. The ratio of the angular velocity of the typebar 132 to that of the front cam assembly 1 11 is, of course, a function of the geometry of the connecting elements. The velocity of the typebar 132 is a function of the angular velocity of the power roll 112 and a variety of other factors including the geometry, mass and spring characteristics and the friction and the duration of the engagement between the cam and the power roll 112. As will be explained more fully hereinbelow the position of the clip 121 on the variable radius bellcrank 122 may be adjusted and thereby change the effective lever arm between holes and 126. When the lever arm is increased, the velocity of typebar 132 will be reduced and when the clip 121 is moved to the right to reduce the lever arm from hole 126 to hole 120 the velocity of typebar 132 will be increased; assuming that all other factors remain fixed or constant.

In its normal or at rest position, the typebar 132 rests on headrest 136 and is biased to that position by spring 137 which has one end attached to the depending arm 131 of typebar 132 while the other end of spring 137 is attached to an appropriate frame member (not shown).

It is also of interest to observe that the counterclockwise pivotal motion of the operating lever 128 will pivot the ribbon lift bar 138 about pivot 139. The pivotal motion of the ribbon lift bar 138 will result in lifting the ribbon (not shown) so that it is placed between the type slug and the document (not shown) when a character is to be printed. In addition, the pivotal motion of the ribbon lift bar will also initiate a carriage escape motion all as more fully set forth in the copending application of Richard W. Allen filed on Nov. 28, 1969, and assigned Ser. No. 880,820 (D-7068) and assigned to the same assignee as the present application.

In normal operation there should be a small clearance between the arm portion 127 of bellcrank 122 and operating lever 128 at the point where they engage each other. To obtain the desired relationship, the bellcrank backstop 141 may be raised or lowered by appropriate adjustment of machine screw and lock nut assembly 142.

A spring 143 biases the front cam assembly 111 for counterclockwise rotation about fulcrum rod 114. The extent of the counterclockwise rotation of the front cam assembly 111 is limited by the position of bellcrank backstop 141. The clearance between cam 115 and power roll 112 may be adjusted by adjusting the effective length of link 118 by turning the adjustable device end of link 118.

It will be seen that bellcrank 122 has an arcuate, approximately radial slot 151, centered on the axis of the pivot point 152 when parts are in their at rest position as illustrated in FIG. 1. Accordingly, moving the clip 121 in the slot 151 does not affect the initial position of the cam assembly 111 or the bellcrank 122. However, as already mentioned, the position of the clip 121 in the closely fitted arcuate slot 151 does control the effective length of the lever arm from hole 126 to hole 120; and therefore the angular rotation of operation lever 128. As an illustrative example, let it be assumed that the cam assembly 111 is pivotally rotated through a specific angle during the engagement of the cam 115 with the power roll 112. The motion of point 152 is then fixed, as is also the motion of the end of link 113 which is engaged in hole 120. When the clip 121 is adjusted in slot 151 so that the hole 120 is a maximum distance from hole 126, a minimum angle of rotation is imparted to bellcrank 122. When the clip 121 is adjusted in slot 151 so that hole 120 is a minimum distance from hole 126 a maximum angle of rotation is imparted to bellcrank 122. At normal operating speeds, these angles of rotation are reflected in corresponding angular velocities. Accordingly, by appropriate adjustment of clip 121 in slot 151 a variety of angular velocities may be imparted to bellcrank 122. The different angular velocities of bellcrank 122 will then cause different angular velocities to be imparted to typebar 132; and the different angular velocities of typebar 132 will result in a corresponding difference in character impression. Accordingly, the character impression may be controlled by the adjustment ofclip 121 in slot 151.

The clip 121 is stamped and formed from a sheet of spring steel. Two holes 123 and 120 are extruded in the clip 121 to form walls 153. The walls 153 serve to position the clip 121 in the slot 151, an in addition, link 118 is coupled to the clip 121 by placing link end 119 through hole 120. In addition, hole 123 is used to position and guide a tool that may be used to selectively position clip 121 in a desired position along slot 151 of bellcrank 122. Or alternatively, link 118 may be coupled in hole 123 to extend the possible range of available lever arms between link 118 and hole 126. In addition, the walls 153 of holes 120 and 123 serve to retain and guide the clip 121 in the arcuate slot 151.

The tongue 154 of clip 121 includes a formed detent 155 which engages the serrations 156 formed on bellcrank 122. At the end of tongue 154 there is a lip 157 which cooperates with a tool (not shown) which may be used to selectively position the clip 121.

As best seen in FIG. 2, the serrations 156 and the detent 155 are so formed as to prevent movement of the clip 121 in the leftward direction (as viewed in any of the figures) without first lifting the detent 155 clear of the serrations 156. The serrations 156 and the detent 155 are designed to prevent leftward movement as that is the natural direction that the applicable forces would tend to move the clip 121 with respect to bellcrank 122. That is, the design is such that the natural and normal forces will not be able to dislodge the clip 121 from the position in which it had been set. In another structure or application, the forces might be such that there would be a natural tendency to move clip 121 to the right. In such a situation the serrations 156 could be formed differently and the detent 155 placed on the right side of tongue 154. Or in some structures it might be desirable to use balanced serations 156. The form of the serrations 156 and the detent 155 will therefore depend upon the exigencies of the specific application.

When it is necessary to move the clip 121 it may be done quite easily. If it is desired to move the clip 121, access thereto may be gained by merely removing a part of the outer casing shown only in outline form at 158. With the case removed there is ready access to the clips 121 on bellcranks 122. If a clip 121 is to be moved to the right, i.e., away from the operator, all that is necessary is to engage a special tool (not shown) in the hole 123 and push gently. Each degree of movement will be readily distinguished by a distinct click as the detent 155 falls into each serration 156. To move the clip to the left, or forward position, it is necessary to raise the detent 155 from the serrations 156. This may be accomplished by a simple tool (not shown) which is somewhat akin to an old-fashioned button book but thinner and with a small projection on one side. The projection is engaged in the hole 123 and then the tool is pivoted about the projection to cause the hook end to enter under lip 157. The hook end thereby raises the tongue 154 and also detent 155 so that it is free of the serrations 156.

Then by a gentle pull on the special tool the clip may be brought as far forward as may be required; or by a gentle push on the tool the clip 121 may be moved to the rear.

As already indicated, moving the clip 121 forward will increase the effective lever arm of bellcrank 122; i.e., the lever arm between holes and 126. With an increased lever arm the typebar 132 will be driven through a smaller angle and experience a reduced acceleration and attain a smaller velocity and thus cause a lighter impression. Opposite results are obtained when the effective lever arm is reduced.

Some prior art techniques required replacing the bellcrank 122 if more than a slight adjustment in character impression was required. The number of difi'erent available bellcranks was quite large and it took considerable experience to select an appropriate one from the many choices available. In addition, the number of optional bellcranks greatly aggravated inventory problems. Many of these problems were solved by the invention disclosed in the cited US. Pat. NO. 3,355,000. However, even with the advantages of the cited patent, there were still 88 individual bellcranks, (see column 5 of said patent). The present invention provides the full range of adjustments with only two bellcranks 122; one for the front side of power roll 112 and one for the rear side of the power roll 112. Obviously, the present invention has greatly simplified the inventory problem. The present invention has also eliminated the time consuming need to change a bellcrank 122 to alter the character impression.

It should be emphasized that the slot 151 is an arcuate slot and more specifically, that the slot 151 is an arc having its center at pivot point 152 when the parts are in an at rest position as shown in FIG, 1. Accordingly, moving the clip 121 will not have any effect on at rest position of cam assembly 111. Prior art impression control techniques used to involve adjustments of the adjustable arm 117 and/or replacement of bellcrank 122. However, any change in link length would have an undesirable effect on the engagement relationship between the cam assemblies 111 and the power roll 112 so that only a very small adjustment could be achieved by this means. Furthermore, the adjustment of element 117 was difficult to make as it is not easily accessible. With the present form of impression control, there should be no need for field adjustment of link 118 or adjustable arm 1 17.

A presently preferred embodiment of the invention has been described above. It will be obvious to those skilled in the art that the link disclosed herein and having a selectively variable lever arm could be used in a wide variety of applications. For example, the link might be used in a structure wherein it is desirable to vary the angular excursion of an output arm. It is believed that no further analysis or description is required and that the foregoing so fully reveals the gist of the present invention that those skilled in the applicable arts can adapt it to meet the exigencies of their specific requirements.

What is claimed is:

1. A selectively adjustable variable radius bellcrank comprising:

a. a pivotally supported bellcrank pivotally movable between an at rest position and an activated position and having first and second crank arms;

b. said first crank arm having first and second surfaces;

c. an arcuate slot in said first crank arm for providing an opening between said first and second surfaces;

serrations disposed on at least part of said first surface of said first crank arm and proximal to said arcuate slot;

e. a clip having a base portion which is wider and shorter than the width and length, respectively, of said arcuate slot for making contact with said second surface of said first crank arm;

f. first an second guide means formed on said base portion of said clip and having a width which is equal to, or slightly less than, the width of said arcuate slot to guide said clip for motion within the confines of said arcuate slot; and wherein g. said clip means includes detent means for coacting with said serrations for retaining said first and second guide means between said first and second surfaces of said first crank arm and at a selected position along the length of said arcuate slot.

2. The combination as set forth in claim 1 wherein said serrations are directionally formed for providing a greater tendency to inhibit the motion of said clip along the path of said arcuate slot in one direction than in the other direction.

3. The combination as set forth in claim 1 and including a link a first and second ends with said first end of said link coupled to said clip for pivoting said bellcrank from its at rest position towards its activated position in response to a longitudinal motion of said link.

4. The combination as set forth in claim 3 wherein at least one of said first and second guide means has a hole therethrough for facilitating the coupling of said link to said clip.

5. The combination as set forth in claim 4 wherein said arcu'ate slot is so oriented with respect to said second end of said link that there is no motion of said bellcrank in response to the movement of said clip on said first crank arm, as guided by the coaction of said first and second guide means within the boundaries of said. arcuate slot, when said second end of said link is pivoted about a fixed point. 

1. A selectively adjustable variable radius bellcrank comprising: a. a pivotally supported bellcrank pivotally moveable between an at rest position and an activated position and having first and second crank arms; b. said first crank arm having first and second surfaces; c. an arcuate slot in said first crank arm for providing an opening between said first and second surfaces; d. serrations disposed on at least part of said first surface of said first crank arm and proximal to said arcuate slot; e. a clip having a base portion which is wider and shorter than the width and length, respectively, of said arcuate slot for making contact with said second surface of said first crank arm; f. first an second guide means formed on said base portion of said clip and having a width which is equal to, or slightly less than, the width of said arcuate slot to guide said clip for motion within the confines of said arcuate slot; and wherein g. said clip means includes detent means for coacting with said serrations for retaining said first and second guide means between said first and second surfaces of said first crank arm and at a selected position along the length of said arcuate slot.
 2. The combination as set forth in claim 1 wherein said serrations are directionally formed for providing a greater tendency to inhibit the motion of said clip along the path of said arcuate slot in one direction than in the other direction.
 3. The combination as set forth in claim 1 and including a link having first and second ends with said first end of said link coupled to said clip for pivoting said bellcrank from its at rest position towards its activated position in response to a longitudinal motion of said link.
 4. The combination as set forth in claim 3 wherein at least one of said first and second guide means has a hole therethrough for facilitating the coupling of said link to said clip.
 5. The combination as set forth in claim 4 wherein said arcuate slot is so oriented with respect to said second end of said link that there is no motion of said bellcrank in response to the movement of said clip on said first crank arm, as guided by the coaction of said first and second guide means within the boundaries of said arcuate slot, when said second end of said link is pivoted about a fixed point. 